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Pleura

The pleura is a thin, double-layered serous membrane that lines the thoracic cavity and covers the lungs. It consists of two continuous parts: the visceral pleura, which tightly adheres to the lung surface and extends into fissures, and the parietal pleura, which lines the thoracic wall, diaphragm, and mediastinum. Between them lies the pleural cavity, a potential space containing a thin film of lubricating fluid that reduces friction during respiration.

Synonyms

  • Pulmonary pleura

  • Visceral and parietal pleura

  • Pleural membrane

Function

  • Provides a smooth frictionless surface for lung expansion and contraction

  • Maintains a negative intrapleural pressure, aiding lung inflation

  • Acts as a protective covering for the lungs

  • Serves as a space for pleural fluid dynamics, important in respiration and pathology

Arterial Supply

  • Parietal pleura: supplied by intercostal arteries, internal thoracic artery, and musculophrenic arteries

  • Visceral pleura: supplied by bronchial arteries (branches of the thoracic aorta)

Venous Drainage

  • Parietal pleura: drains into intercostal veins and internal thoracic veins

  • Visceral pleura: drains into bronchial veins, which empty into the azygos and hemiazygos systems

Nerve Supply

  • Parietal pleura: richly innervated (pain-sensitive) by intercostal nerves (costal pleura, peripheral diaphragmatic pleura) and phrenic nerves (mediastinal pleura, central diaphragmatic pleura)

  • Visceral pleura: autonomic innervation via the pulmonary plexus; insensitive to pain

MRI Appearance

T1-weighted images:

  • Normal pleura is extremely thin and usually not visualized unless thickened

  • When visible, it appears as a low signal intensity line bordering hyperintense fat or lung tissue

  • Pleural effusions appear low-to-intermediate signal depending on protein content

T2-weighted images:

  • Pleura itself: thin hypointense line

  • Pleural effusion: hyperintense (fluid)

  • Inflammatory or tumorous pleural thickening may appear as intermediate-to-high signal intensity

STIR (Short Tau Inversion Recovery):

  • Fat suppression improves visualization of pleural abnormalities

  • Normal pleura is low signal; edema, infection, or tumors appear hyperintense

  • Pleural effusions stand out as bright signal collections

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal pleura shows minimal enhancement

  • Abnormal thickening (e.g., pleuritis, mesothelioma, metastases) demonstrates heterogeneous or nodular enhancement

  • Useful for differentiating benign vs malignant pleural disease

CT Appearance

Non-contrast CT:

  • Normal pleura is too thin to be seen; appears only when thickened or calcified

  • Pleural calcifications are hyperdense, commonly from asbestos exposure or old infections

  • Pleural effusions: appear as homogeneous hypodense fluid collections

Contrast-enhanced CT (CECT):

  • Pleural thickening or masses enhance variably

  • Malignant pleural disease shows nodular, circumferential, or irregular enhancement

  • CECT is excellent for evaluating pleural effusions, empyema, mesothelioma, and pleural metastases

MRI image

Pleura anatomy MRI coronalL image -img-00000-00000

CT image

Pleura anatomy CT AXIAL image -img-00000-00000